Ground-based optical long-baseline interferometry has the power to measure the orbits of close binary systems at ~10 micro-arcsecond precision. This precision makes it possible to detect "wobbles" in the binary motion due to the gravitational pull from additional short period companions. We started the ARrangement for Micro-Arcsecond Differential Astrometry (ARMADA) survey with the MIRC-X instrument at the CHARA array for the purpose of detecting giant planets and stellar companions orbiting individual stars in binary systems. We describe our observations for the survey, and introduce the wavelength calibration scheme that delivers precision at the tens of micro-arcseconds level for <0.2 arcsecond binaries. We test our instrument performance on a known triple system kappa Peg, and show that our survey is delivering a factor of 10 better precision than previous similar surveys. We present astrometric detections of tertiary components to two B-type binaries: a 30-day companion to alpha Del, and a 50-day companion to nu Gem. We also collected radial velocity data for alpha Del with the Tennessee State University Automated Spectroscopic Telescope at Fairborn Observatory. We are able to measure the orbits and masses of all three components in these systems. We find that the previously published RV orbit for the inner pair of nu Gem is not consistent with our visual orbit. The precision achieved for these orbits suggests that our ARMADA survey will be successful at discovering new compact triple systems to A/B-type binary systems, leading to better statistics of hierarchical system architectures and formation history.

中文翻译：

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无敌舰队。I. 在 B 型双星 α Del 和 ν Gem 中检测到三重伴星

地基光学长基线干涉仪能够以~10 微角秒的精度测量紧密双星系统的轨道。由于来自附加短周期伴星的引力，这种精度使得检测双星运动中的“摆动”成为可能。我们开始使用 CHARA 阵列上的 MIRC-X 仪器进行微弧秒微分天体测量 (ARMADA) 测量，目的是探测双星系统中围绕单个恒星运行的巨行星和恒星伴星。我们描述了我们对调查的观察结果，并介绍了波长校准方案，该方案可为 <0.2 角秒的二进制提供数十微角秒级别的精度。我们在已知的三重系统 kappa Peg 上测试我们的仪器性能，并表明我们的调查提供的精确度比以前的类似调查高 10 倍。我们向两个 B 型双星展示了三次分量的天体测量检测：一个 alpha Del 的 30 天伴星，以及一个 nu Gem 的 50 天伴星。我们还使用费尔伯恩天文台的田纳西州立大学自动光谱望远镜收集了 alpha Del 的径向速度数据。我们能够测量这些系统中所有三个组件的轨道和质量。我们发现之前公布的 nu Gem 内部一对的 RV 轨道与我们的视觉轨道不一致。这些轨道达到的精度表明，我们的 ARMADA 调查将成功地发现新的紧凑三重系统到 A/B 型双星系统，从而更好地统计分层系统架构和形成历史。